Title:
【発明の名称】干渉計
Document Type and Number:
Japanese Patent JP2979701
Kind Code:
B2
Abstract:
PURPOSE:To reduce the change in the difference of light passage lengths generated due to temperature variation by satisfying a specified expression for the physical length of a light passage length correction block. CONSTITUTION:A physical length 1i of a light passage length correction block is set so that an expression 1 is satisfied for di, where ni is refractive index, di is the change in the physical lengths between two beam luminous fluxes for each medium, alphai is rate of change in unit length due to expansion and contraction of the medium except for air, and T is temperature. An interferometer has, for example, a prism P1 which is the light passage length correction block, a prism P2 which is a reflection mirror for bending the light passage, and a polarizing beam splitter 2 which is a beam splitter. Difference in the prism lengths in the proceeding direction of the divided two luminous fluxes is L1, and a distance between the two luminous fluxes is L2. The material of glass is BK7, the wavelength is 632.8nm, and the temperature is 25 deg.C. alpha=7.1X10<-6>/K, n=1.515 (n=n2/n1, where n1 is refractive index of air, and n2 is refractive index of glass). L1=2.1XL2, and when L2=20mm, for example, L1=42mm.
Inventors:
SUEYOSHI MASASHI
Application Number:
JP9195291A
Publication Date:
November 15, 1999
Filing Date:
April 23, 1991
Export Citation:
Assignee:
NIKON KK
International Classes:
G01B9/02; G01J3/45; (IPC1-7): G01B9/02
Domestic Patent References:
| JP63228003A | ||||
| JP1178804A |
Attorney, Agent or Firm:
Sanshin Iwao (2 people outside)